Transformation of a Mononitrosyl Iron Complex to a [2Fe-2S] Cluster by a Cysteine Analogue

• Published in: Journal of the American Chemical Society 2014-05, Vol.136 (20), p.7229-7232
• Main Authors: Fitzpatrick, Jessica, Kalyvas, Harris, Filipovic, Milos R, Ivanović-Burmazović, Ivana, MacDonald, John C, Shearer, Jason, Kim, Eunsuk
• Format: Article
• Language: English
• Subjects: Cysteine - analogs & derivatives; Cysteine - chemistry; Iron - chemistry; Iron-Sulfur Proteins - chemistry; Models, Molecular; Molecular Conformation; Nitrogen Oxides - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja5024207

Reversible modification of iron-sulfur clusters by nitric oxide acts as a genetic switch in a group of regulatory proteins. While the conversion of [Fe-S] clusters to iron-nitrosyls has been widely studied in the past, little is known about the reverse process, the repair of [Fe-S] clusters. Reported here is a system in which a mononitrosyl iron complex (MNIC), (PPN)[Fe(S t Bu)3(NO)] (1), is converted to a [2Fe-2S] cluster, (PPN)2[Fe2S2(SCH2CH2C(O)OMe)4] (2). This conversion requires only the addition of a cysteine analogue, 3-mercaptomethylpropionate (MMP), at room temperature without the need for any other reagents. The identity of 2 was confirmed spectroscopically, chemically, crystallographically, and analytically. Mass spectrometry and 34S labeling studies support that the bridging sulfides in 2 derive from the added MMP, the cysteine analogue. The NO lost during the conversion of 1 to 2 is trapped in a dinitrosyl iron side product, (PPN)[Fe(SCH2CH2C(O)OMe)2(NO)2] (4). The present system implies that MNICs are likely intermediates in the repair of NO-damaged [2Fe-2S] clusters and that cysteine is a viable molecule responsible for the destabilization of MINCs and the formation of [2Fe-2S] clusters.